EP3309422A1 - Cooled flywheel - Google Patents

Abstract

This flywheel (1) of a thermal engine of a vehicle comprises a ring of inertia (2) comprising a cooling means. This cooling means comprises cooling ducts (3) by centrifugation of air passing through the ring (2), the channels (3) comprising an air passage section and heat-sensitive means (4) of variation of this section. , the heat-sensitive means (4) closing these sections when a temperature of the heat-sensitive means (4) is below a low temperature threshold.

Description

The invention relates to the field of motor vehicle powertrains. Even more particularly, the invention relates to the cooling of dry clutches, in particular the cooling of a flywheel coupled to this clutch.

A clutch is a mechanical system providing a coupling between a heat engine and a gearbox (mechanical or driven). It comprises for this purpose a flywheel, at least one friction disk (or clutch), and a pressure mechanism (comprising at least a pressure plate and a clutch bell or cover, and a possible diaphragm) . The flywheel (which can be single or double) is intended to be secured to a shaft of the engine, for example its crankshaft. The friction disk is intended to be secured to a primary shaft of the gearbox. The pressure plate (of the pressure mechanism) is responsible for pressing the friction disk against the flywheel when it is pushed by a member such as a diaphragm under the action of a stop, itself actuated by a clutch control. The cover (of the pressure mechanism) makes it possible to firmly secure the latter to the flywheel. The pressure mechanism comprises in its lid and / or in its possible diaphragm first openings for the entry of air and peripheral openings for the output of this air in the vicinity of the flywheel / cover junction.

The torque that is produced by the heat engine is first transmitted to the flywheel via the crankshaft (through its rotational movement), then to the friction disc and finally to the primary shaft of the gearbox.

As known to those skilled in the art, in certain life situations, the temperature increase of the clutch parts that are involved in the friction (pressure mechanism, flywheel and friction disc) may exceed one high threshold beyond which there is a degradation of the torque transmission, or even a deterioration of some parts, requiring to provide their cooling.

However, these parts are not very accessible, and confined between the engine and the gearbox, making their cooling easy because the air flow is limited.

This difficulty proves even more problematic when one wishes to obtain an extension of the ratios of the gearbox, in particular with the aim of reducing the consumption of energy (and thus the production of CO ₂ ). Indeed, the lengthening of these ratios leads to greater stress on the clutch, which requires strengthening of its parts and an adaptation of the forms of the latter that it is increasingly difficult to obtain.

Conversely, when the temperature of the clutch parts that are involved in the friction (pressure mechanism, flywheel and friction disk) is below a low threshold (for example, when traveling in cold climatic conditions or after a prolonged stop), a limitation of the torque transmission is observed by a phenomenon of cold slip of the friction disk.

The patent FR-B-2 974 868 discloses a thermal protection strategy integrated in software either in the computer supervising the engine (and generally called "Multifunction Motor Control" (or CMM)) when the gearbox is manual type or in the actuator box when the latter is controlled. It takes into account the temperature measurement of the pressure plate, which is estimated continuously throughout the life of the vehicle. When certain temperature thresholds are reached, protections are put in place, for example by activating the motor-fan unit and / or modifying the depression mapping of the accelerator pedal, in an attempt to reduce the temperature of the plateau of pressure.

This solution temporarily prolongs misuse of the clutch and thus slightly reduce the temperature of the air inside the housing, but limits the performance of the vehicle and little improves the cooling of the clutch parts that are involved in the friction, because the motor-fan unit remains a means of external cooling to the clutch.

The patent FR-B-2,806,766 discloses a flywheel having a generally annular friction surface, wherein the flywheel, at least radially inside the friction lining, is equipped with vanes so as to produce, during its rotation, a flow of air which flows along its opposite side to the friction lining.

This solution allows effective cooling of the flywheel, but it does not adapt to driving situations in cold weather conditions, this cooling being permanently linked to the rotation of the flywheel.

There is therefore a need for effective cooling when the temperature of the clutch parts that are involved in the friction exceeds the high threshold, and which also satisfies the cold climatic conditions.

The invention aims to provide a flywheel overcoming the problem of the state of the art mentioned above, ensuring proper operation in various conditions, including winter.

For this purpose, the invention proposes an inertia flywheel of a heat engine of a vehicle, this flywheel comprising a ring of inertia comprising a cooling means. This flywheel is such that the cooling means comprises air centrifugal cooling channels passing through the ring, the channels comprising an air passage section and heat-sensitive means of variation of this section, the heat-sensitive means closing these sections. when a temperature of the heat-sensitive means is below a low temperature threshold.

In fact, the heat-sensitive means of the cooling channels make it possible to act on the cooling air passage section, thereby regulating a cooling air flow rate, and thus cooling. When the passage section is closed below the low temperature threshold, it avoids cooling the steering wheel and makes it possible to adapt to driving situations in cold climatic conditions. In particular, when the steering wheel turns during cold weather conditions and as long as the temperature is below the low temperature threshold, the cooling is stopped.

In addition, the channels passing through the ring, when their passage section is open or partially open (and therefore when the temperature is above the low temperature threshold), they allow to cool the steering wheel in the heart of its material, increasing and the efficiency of cooling, and thus enhance the ring by adding a cooling function in addition to its inertia function, support of a starter ring or interface with a clutch bell.

It will be noted that the temperature is the temperature at the level of the heat-sensitive means, that is to say the temperature of the ring by thermal conduction on the thermosensitive medium, or the temperature of the air passing through the channels by convection on the medium. thermosensitive, or a distribution between conduction and convection.

Note also that this invention applies both to a single flywheel (a single steering wheel) to a double damping flywheel (two flywheels elastically connected).

Advantageously, the low temperature threshold is between 50 ° C and 250 ° C.

According to one embodiment, the heat-sensitive means comprise a thermo-deformable material forming a valve.

Indeed, this embodiment is very simple and easy to integrate into the channels. The deformation of the valve caused by the heat, will gradually open it as soon as the increasing temperature exceeds the low threshold.

According to a particular characteristic of the invention, the thermo-deformable material is a metal alloy with shape memory.

According to one embodiment, the channels are oriented radially to the ring.

Indeed, the radial orientation of the channels allows a good centrifugation of the air contained in the channels when the wheel rotates, and allows the cooling of the steering wheel when the passage section of the channels is free again.

In one embodiment, the inertia ring has a generally annular friction surface, and the channels are housed in an extra thickness of the ring, this extra thickness forming a peripheral extension of the friction surface.

Indeed, the friction surface between the ring and the lining of a clutch disk is the hottest surface of the flywheel, and it is advantageous for the cooling channels to be close to this surface. warmer to have an effective cooling (large temperature difference between this zone and the air passing through the channels), and also to have a good sensitivity and a good reactivity of the thermosensitive medium, since the temperature of the friction surface is one of the parameters that condition the adhesion of the clutch disc lining to the friction surface. The peripheral extension of the friction surface makes it possible to position the channels and the heat-sensitive means near this hottest surface of the flywheel.

In addition, the extra thickness makes it possible to have channels opening at each of their ends (upstream and downstream) while being rectilinear. Indeed, the extra thickness allows a good air circulation inside the channels because it allows to position the channels in a plane shifted from that of the friction surface of the steering wheel, but also offset from the planes of the friction surfaces d a clutch disk associated with the steering wheel. Thus, the clutch disc is no longer an obstacle to the passage of air in the channels.

It should be noted that this invention applies in the same way to multi-disk clutches.

It will be understood throughout the text of this document by upstream and downstream end, the ends of the channels in the direction of the passage of air, that is to say the end near the center of rotation of the steering wheel for the end upstream, and the end at the periphery of the steering wheel for the downstream end.

It will also be noted that the peripheral extension of the friction surface makes it possible to house the channels in a portion of the steering wheel where its peripheral speed is greatest, which, for the centrifugation of the air, is an optimal condition of efficiency.

According to one embodiment, this extra thickness forming a peripheral extension of the friction surface comprises a large outer diameter, and a small inside diameter, and the heat-sensitive means housed in the channels are positioned on this small inside diameter.

Indeed, the heat-sensitive means are thus positioned closer to the friction surface, that is to say where the temperature of the extra thickness is greatest. This increases the sensitivity and response time of the thermosensitive medium.

According to one embodiment, the heat-sensitive means are inserted into force in the channels.

According to an alternative embodiment, the heat-sensitive means are overmolded in the channels.

According to one embodiment, the flywheel comprises a connecting hub integral with the inertia ring, and is such that the hub comprises complementary cooling channels by air centrifugation therethrough.

Indeed, these complementary channels allow additional air circulation.

According to one embodiment, the complementary channels comprise a thermosensitive complementary means of variation of their passage section.

The invention also relates to a motor vehicle comprising a powertrain with a clutch and a flywheel, the flywheel being as briefly described above.

• la figure 1 est une vue d'un volant à inertie selon un mode de réalisation de l'invention.
• la figure 2 est une vue partielle agrandie de la figure 1, montrant un canal de refroidissement avec un moyen thermosensible.
• la figure 3 est une vue schématique en coupe d'un volant à inertie selon un mode de réalisation, avec une partie de son environnement.
• la figure 4 est une vue d'un volant à inertie selon un mode de réalisation de l'invention.

La figure 1 est une vue d'un volant à inertie 1 d'un moteur thermique d'un véhicule selon un mode de réalisation de l'invention. Le volant à inertie 1 comprend un anneau d'inertie 2. Cet anneau d'inertie 2 comprend un moyen de refroidissement sous la forme de canaux de refroidissement 3 par centrifugation d'air. Ces canaux 3 traversent l'anneau 2, et comprennent une section de passage d'air et des moyens thermosensibles 4 de variation de cette section. Les moyens thermosensibles 4 ferment ces sections lorsqu'une température des moyens thermosensibles 4 est en dessous d'un seuil de température bas.Other features and advantages of the present invention will be better understood with the help of the description and non-limiting drawings, among which:

• the figure 1 is a view of a flywheel according to one embodiment of the invention.
• the figure 2 is an enlarged partial view of the figure 1 , showing a cooling channel with a thermosensitive means.
• the figure 3 is a schematic sectional view of an inertial flywheel according to one embodiment, with part of its environment.
• the figure 4 is a view of a flywheel according to one embodiment of the invention.

The figure 1 is a view of a flywheel 1 of a thermal engine of a vehicle according to one embodiment of the invention. The flywheel 1 comprises a ring of inertia 2. This ring of inertia 2 comprises a cooling means in the form of cooling channels 3 by air centrifugation. These channels 3 pass through the ring 2, and include an air passage section and thermosensitive means 4 for varying this section. The heat-sensitive means 4 close these sections when a temperature of the heat-sensitive means 4 is below a low temperature threshold.

This low temperature threshold causing the closure of the air passage sections when the temperature of the heat-sensitive means 4 is below this threshold, is between 50 ° C and 250 ° C.

Indeed, measurements of temperature rise of a flywheel in the context of a test of the "follow-up" type, that is to say a repeated start and stop test in a traffic jam, have shown that the temperature of the air around the Inertia flywheel reaches a value of 195 ° C when the flywheel reaches a temperature of 330 ° C and a pressure plate (which will be described in figure 3 ) reaches a temperature of 390 ° C. These values are critical values for the operation of a clutch in contact with a friction surface. As soon as the temperature of the heat-sensitive means 4 is above the threshold, the air passage sections are thus opened to cool the steering wheel. with inertia 1, so as to avoid the critical temperature of 330 ° C of the flywheel 1.

Conversely, the heat-sensitive means 4 are designed to close or reduce the passage section when the temperature of the flywheel and / or air passing through the channels 3 drops below this threshold, so as to avoid temperatures. Low flywheel 1 in winter conditions.

Indeed, when the temperature is below this low threshold (for example, when driving in cold climatic conditions or after a prolonged stop), a limitation of the transmission of the torque is observed by a phenomenon of cold skating. a friction disk (or clutch plate). In particular, tests in cold conditions, have shown that with negative temperatures, for example -15 ° C, a maximum torque transmissible by the friction disc can be reduced from 10 to 20%.

In addition, especially for diesel engines, the flywheel 1 may comprise two masses linked together by springs. One of the masses is integral with a crankshaft and the other mass is integral with a transmission, the two being connected by cleats, a ball bearing and springs. This is a damping device absorbing excessive variations in kinetic energy, thus reducing the torsional stress of the transmission. These springs are housed in cavities lined with grease. In conditions of very low temperature, especially below 0 ° C, this grease freezes and can impede the proper operation of the flywheel. It is therefore useful to allow the clutch to quickly reach a temperature range adequate to the proper operation of the flywheel, such as greater than 0 ° C, preferably greater than 40 ° C.

In operation, the rotation of the flywheel 1 has the effect of generating a forced circulation by centrifugation of the air through the channels 3 favorable to a heat exchange. The air thus heats up by convection along the channels to be ejected by centrifugation at the periphery of the flywheel 1, the heat-sensitive means regulating the flow of air as a function of the temperature of the flywheel and / or air.

The heat-sensitive means 4 comprise a thermo-deformable material forming a valve. The thermo-deformable material is, for example, a shape-memory metal alloy, commonly designated by the acronym AMF, which makes it possible to alternate between two forms previously stored when its temperature varies around a critical temperature, namely the temperature threshold. low. There are known alloys with these properties, such as Cu-Al-Ni, Cu-Al-Zn or Ni-Mn-Ga alloys which are alloys for use in this invention.

The channels 3 are oriented radially to the ring 2, so as to ensure the centrifugation of the air contained in these channels 3. A channel may form an inclination angle of 0 to 30 degrees relative to the radius of the ring 2 crossing it. Here there are 10, but can be between 2 and 30. Increasing their number increases the cooling potential of the cooling means.

The figure 1 further shows a starter ring 100 integral with the ring 2, which can be fixedly attached to the ring 2, a hub 7 integral with the ring 2 and allowing an interface with a crankshaft of the heat engine, fixing holes 102 traversing the hub 7 axially and allowing the passage of fastening screws which perform the assembly of the hub 7 on the crankshaft. Note also the screws or studs 101, which serve as fixing for the assembly of a clutch bell on the ring 2.

The ring of inertia comprises the generally annular friction surface 5, and the channels 3 are housed in an excess thickness 6 of the ring 2, this extra thickness 6 forming a peripheral extension of the friction surface 5. This friction surface is is then delimited at its periphery by the extra thickness 6, and in its center by the hub 7.

The thermosensitive means 4 are housed in the upstream end of the channels 3. It is indeed advantageous for the thermosensitive means 4 to be close to the friction surface 5, this surface being a hottest area of the flywheel 1, for effective cooling (large temperature difference between this area and the air flowing through the channels), and also to have a good sensitivity and a good reactivity of the thermosensitive means, since a temperature of the friction surface 5 is one of the parameters which condition the adhesion of the lining of a clutch disk to the friction surface 5.

The figure 2 shows a channel 3 in the excess thickness 6 which is partially closed by the thermosensitive means 4 which here has a form of valve. This valve is a shutter controlled by the shape memory alloy, which under the action of the elevation of the temperature of the flywheel 1 and / or air, will open the shutter. The shutter can be the shape memory alloy itself. The thermosensitive means 4 is forcefully inserted into the channel 3, being blocked by a tight fit between the thermosensitive means 4 and the passage section. In a variant, the thermosensitive means 4 is overmolded in the channel 3, during a casting of the ring 3.

The figure 3 is a schematic sectional view of the flywheel 1 according to one embodiment. The hub 7, the ring 2 and the excess thickness 6 are made in one piece, for example by casting. The starter ring 100 is attached to the flywheel 1. There is shown a channel 3 in section, and the thermally sensitive valve 4 which is a flap with an inclination angle ALPHA with respect to the axis of the channel 3. This ALPHA angle will evolve with the temperature of the flywheel and / or air, to open or close depending on whether one is respectively above the low temperature threshold or below.

This figure shows the clutch disc 103 in position on the friction surface 5, this clutch disc 103 being covered with friction material on its two faces in contact, respectively, with the friction surface 5 of the flywheel 1 and another friction surface on the pressure plate 107, the pressure plate 107, a pressure mechanism 105, and the clutch bell 104 attached to the ring 2 by the studs 101.

The pressure plate is controlled by a lever type control mechanism with a clutch abutment and a diaphragm (not shown), the lever being supported on a clutch housing (not shown). The clutch housing essentially comprises a wall forming an enclosure housing the flywheel 1, the clutch housing 104, the clutch disk 103, the pressure plate 107. The flywheel 1 and the pressure plate 107 are integral in rotation with the crankshaft, and are thus indexed in rotation relative to each other . The clutch disk 100 is integral in rotation with a primary shaft of a gearbox fixed to the clutch housing.

Conventionally, the lever tilts around a pivot joint and / or ball carried by the clutch housing, pushing the diaphragm via the clutch abutment, diaphragm which then compresses the pressure plate 107 by translating it against the pressure mechanism 105, thus releasing the clutch disc 103 and uncoupling the primary shaft from the crankshaft. This operating principle is well known in itself to those skilled in the art.

The excess thickness 6 judiciously makes it possible to unclamp the upstream section of the channel 3 from the thickness of the lining of the friction disk 100. In this way, the air contained in the enclosure of the clutch housing can freely pass through the section. upstream of canal 3.

In a variant, and if necessary, an indentation is made vis-à-vis the upstream section of the channel 3 in the pressure plate 107. Indeed, the pressure plate 107 is always at the same angular position relative to the flywheel. inertia 1 because they are integral in rotation to one another (via the clutch bell). This notch 107 will therefore always be vis-à-vis the upstream section of the channel 3, which would not have been possible if this notch was made in the thickness of the lining of the clutch disc 103.

The figure 4 is an inertia flywheel according to one embodiment. The flywheel 1 comprises the connecting hub 7 integral with the inertia ring 2, and the hub 7 comprises complementary channels 8 cooling air centrifugation therethrough. These complementary channels 8 are provided with a thermosensitive complementary means of variation of their passage section, the technical definition of which is identical to that of the thermosensitive means 4.

Claims (10)

Inertia flywheel (1) of a thermal engine of a vehicle, said flywheel (1) comprising an inertia ring (2) comprising a cooling means, characterized in that said cooling means comprises cooling channels ( 3) by centrifugation of air passing through said ring (2), said channels (3) comprising an air passage section and heat-sensitive means (4) of variation of said section, said heat-sensitive means (4) closing said sections when a temperature of said heat-sensitive means (4) is below a low temperature threshold. Flywheel according to claim 1, characterized in that said heat-sensitive means (4) comprise a thermo-deformable material forming a valve. Flywheel according to claim 2, characterized in that said thermo-deformable material is a metal alloy with shape memory. Flywheel according to one of the preceding claims, characterized in that said channels (3) are oriented radially to said ring (2). Flywheel according to claim 4, said inertia ring having a friction surface (5) generally annular, characterized in that said channels (3) are housed in an excess thickness (6) of said ring (2), said extra thickness ( 6) forming a peripheral extension of said friction surface (5). Flywheel according to one of the preceding claims, characterized in that said heat-sensitive means (4) are forcefully inserted into said channels (3). Flywheel according to one of claims 1 to 5, characterized in that said heat-sensitive means (4) are overmolded in said channels (3). Flywheel according to one of the preceding claims, said flywheel comprising a connecting hub (7) integral with said inertia ring (2), characterized in that said hub (7) comprises complementary channels (8). cooling by centrifugation of air passing through it. Inertia flywheel according to claim 8, characterized in that said complementary channels (8) comprise a thermosensitive complementary means of variation of their passage section. Motor vehicle comprising a power unit with a clutch and a flywheel, characterized in that the flywheel is according to one of the preceding claims.

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